How to Calculate Gallons in a Propane Tank | Hunker- 35 000 Litres LPG Tank Truck LPG Transport ,Propane tanks are portable storage containers that hold and transport propane gas. Propane gas is generally expressed in gallons and propane tanks can hold a specified maximum number of gallons of propane gas when full.Sizes & Specifications - Burden PropanePropane Cylinder Dimensions (may vary by manufacturer). 5 LB Cylinder 12″ X 8 1/2″ 11 LB Cylinder 17 1/2″ X 9″ 20 LB Cylinder